Fulminating fuse



H. SELVIDGE FULMINATING FUSE Feb. 21,1950

Filed July 31, 1947 FIG. 2

INVENTOR.

' HARNER SELVIDGE BY remnant. 21, 1950 uurrao STATES PATENT orrica- FULMINATING FUSE Earner Selvidge, Hohokus, N. 1., assignor to the United States of America as represented by the Secretary of the Navy Application July 31, 1947, Serial No. 765,103

Th s invention relates to fulminating fuses, also known as fulminating cords, which have the characteristic that a fulminating impulse is transmitted therethrough at extremely high velocity, and has particular relation to fuses of this type which are suitable for use in electrically operated fuzes employed in ignition-detonated ordnance missiles such as projectiles, bombs, torpedoes, mines and the like.

One type of conventional fulminating fuse consists of a core of trinitrotoluene enclosed in a lead covering. This type of fuse has been in part superseded by a fulminating fuse comprising a high explosive core of pentaerythritetetranitrate contained within a waterproof sheath overlaid by reinforcing coverings. The latter fuse has been generally preferred because of its comparative ability to withstand rough usage without physical damage, and because of its flexibility, positive action and ease of handling. Conventional fulminating fuses have certain disadvantages which make them unsuitable for use in the operationand demolition of delicate devices such as electrically operated fuzes where flexibility, minimum size, ruggedness, positive action, low explosion temperature and minimum space requirements are of prime importance.

One of the disadvantages of conventional fuses is that the fulminating composition is relatively brittle and subject to fracture when the fuse cord is bent or flexed. Such breaking or fracturing may disjoint the fulminating cord so as to interrupt continuous fulmination of the fuse train and thereby prevent passage of the fulmi natng wave past the fractured portion. Another objection to prior known fulminating fuses is that the fulmination temperature of the explosive components is too high for use as a fuse train embedded in a container of plastic having a low melting temperature or a low ignition temperature without causing physical deformation of the container upon fulmination.

A principal object of the present invention is to provide a fulminating fuse which will possess the physical characteristics of flexibility, ruggedness and positive action.

Another object of the invention is to provide a fulminating fuse which is capable of being bent and flexed without fracturing, kinking or disjointing.

A further object of the invention is to provide a fulminating fuse which will have a low explosion temperature.

These and other objects of the invention will so 2 i be understood by reference to the following descrlption and accompanying drawing in which: Fig. 1 is a cross-sectional view of a preferred embodiment of the fulminating fuse of the presi cut invention, on plane l of Fig. 2, and

Fig. 2 is a side view of a fragment of the fuse, with the outer covering in longitudinal section,

to show the braided cord.

It will be understood that the drawings show the structure on a very greatly enlarged scale.

Referring to the drawing, the fulminating fuse in a preferred form includes a continuous, flexible line It which is shown in the form of a braided cord or multi-strand string. While ordinary textile lines have been satisfactorily used, lines of synthetic textiles, glass lines or metallic wires of suitable flexibility and tensile strength are also satisfactory. The line I0 is impregnated and coated with a plastic fulminating composition II which serves not only to fill the numerous interstices occasioned by the use of the multi-strand line l0, but also completely encloses it. The plastic fulminating composition Ii preferably includes barium azide as the explosive component thereof although other explosive primer compounds or mixture may be used. Barium azide is preferred because it has a low explosion temperature in the neighborhood of 150 C. This characteristic makes it possible to employ the present fulminating fuse in a low melting temperature type plastic component of a fuze or the like without softening or burning the adjacent plastic.

While nitro starch dissolved in acetone has been successfully used as a plasticizer, other plastic compositions may be used. A binder l2 consisting of non-continuous, fibrous threads is incorporated in the plastic fulminating composition II while the latter is in a plastic condition in such a, manner as to form a continuously arranged series of fibers oriented substantially parallel with the line ill. By mechanically reinforcing the fulminating composition in this manner, the flexibility and pliability thereof is improved and the likelihood of breaks and fractures is reduced. In the event that a break or fracture does occur, the binder threads l2 form bridges or links which serve to maintain the sides of the fracture in contact so as to permit uninterrupted travel of the fulminating wave along the length of the fuse. The binder threads 62 are preferably composed of felted fibers or other long-fiber material such as macerated cotton threads, cotton linters, natural wool threads, asbestos fibers, glass wool, or the like.

One satisfactory method of impregnating and coating which may be employed is conventional string coating such as is used in the coating of wire, rope, string and the like with protective plastic coatings. If desired, the finished fulminating fuse may be overcoated in the same manner with a protective coating ii for the purpose of making the fuse water and moisturevapor impervious.

The fulminating cord of the present invention has found particular-application as a fuse train embedded in a low temperature plastic container.

What is claimed is: L

A fulminating fuse capable, when embedded in low-melting plastic material, or fulminating without heat-injury to said material, said fuse including a highly flexible and relatively smalldiameter core 01 continuous braided material impregnated and coated with a plastic fulminating composition containing finely-divided barium azide mixed with a binder consisting substantially of longitudinally-extending, non-continuous, reinforcing fibers embedded in said plastic fulminating composition, whereby the heat generated upon fulmination is relatively small due to the low temperature of ignition of the barium azide and the small diameter of the core, while at the same time said small diameter in cooperation with the presence of the fibrous reinforcing threads prevents fracture of the iulminating composition upon sharp fiexure of the core.

HARNER SELVIDGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,128,394 Wohler Feb. 16, 1915 2,004,956 Martin June 18, 1935 2,113,004 Snelling Apr. 5, 1938 2,239,051 Pearsall et a1. Apr. 22, 1941 2,369,583 Lucid Feb. 13, 1945 

